(a). Field of the Invention
The present invention relates to communication systems, and more particularly to a start-up procedure of a communication system.
(b). Description of the Prior Arts
In a general communication system, in order to correctly receive data in the receiving side, functional blocks of the receiver usually are trained. In the start-up procedure of the communication system, lots of parameters of the functional blocks need to be properly configured so as to make the receiver receive the data correctly. In order to properly configure these parameters, the known signals issued from the transmitting side are needed, i.e. in a data-directed manner, so as to enable the receiver to progressively find the proper parameters for the functional blocks.
However, in some communication systems, e.g. IEEE 802.3ab (i.e. 1000 Base-T) or IEEE 802.3an (i.e. 10G Base-T) Ethernet, the parameters of the functional blocks are trained in a decision-directed manner to get the proper parameters. Nonetheless, the functional blocks may operate to influence each other such that the parameters of the functional blocks can not converge to proper values in the training process and thus the receiver can not correctly receive the signals transmitted from the transmitter. Therefore, the transceivers in these communication system need a start-up method to rapidly and stably train the related functional blocks in their receivers, so as to assure that the receivers can correctly receive the data transmitted from the transmitter of the other side.
Besides, Ethernet is a communication system which follows the IEEE 802.3ab or IEEE 802.3an standard having a master-slave architecture in the start-up procedure, wherein four pairs of transceivers perform communication simultaneously. Each pair of transceivers includes one master transceiver and one slave transceiver, and performs communication via a channel. Since the transmission and reception of signals are performed simultaneously in the same channel, a transceiver will receive the signal transmitted by a far-end transceiver and the echo signal resulted from the transmission signal of the transceiver itself. Besides, since the IEEE 802.3ab or IEEE 802.3an Ethernet performs data transmission via four channels simultaneously, the transceiver for one channel will further receive the cross-talks resulted from the transmission signals within other three channels, as shown in FIG. 1. FIG. 1 shows four pairs of transceivers, where each transceiver includes a transmitter TX, a receiver RX and a hybrid circuit. For each transceiver (the transceiver 11 are taken as example in FIG. 1), in addition to the transmission signal from the transmitter of the far-end transceiver 12, the receiver also receives the echo resulted from the transmission signal of the own transmitter, the near-end cross talks (NEXT) resulted from the transmission signals of the transmitters of the other near-end transceivers 13, 14 and 15, and the far-end cross talks (FEXT) resulted from the transmission signals of the transmitters of the other far-end transceivers 16, 17 and 18. In particular, in the IEEE 802.3an Ethernet standard, the transmission rate is largely increased to near the transmission capability limit of the channel, so the far-end cross talks are significant and need an effective mechanism to do cancellation. In sum, since at least one of the interferences such as echoes, near-end cross talks and far-end cross talks impact the performance of data reception of the transceiver, it would be an important issue about how to train the interference cancellers in the transceiver during the start-up procedure of the transceiver so as to get the proper parameters within a predetermined period of time.